1. Field of the Invention
The present invention relates to a flash memory device and a fabricating method thereof.
2. Description of the Related Art
There are various kinds of semiconductor memory devices. Among them, flash memory devices are drawing attraction. A flash memory device will be described below.
FIGS. 1 to 3 are plan views illustrating sequential procedures of fabricating a related art flash memory device, and FIGS. 4 to 6 are sectional views taken along line A-A′ of FIGS. 1 to 3, respectively.
Referring to FIGS. 1 and 4, trench insulating layers 12 are formed on a silicon substrate 10 to thereby define an active region 13. That is, the active region 13 is defined as a region where the trench insulating layers 12 are not formed.
Referring to FIGS. 2 and 5, a floating gate 14 is formed in the active region 13 on the silicon substrate 10. The floating gate 14 is formed by depositing a conductive layer on an entire surface of the silicon substrate 10 and patterning the deposited conductive layer. A reference numeral 15 represents a selection gate.
Referring to FIGS. 3 and 6, an interlayer insulating layer 16 and a control gate 18 are formed on the floating gate 14. The interlayer insulating layer 16 may be an oxide/nitride/oxide (ONO) layer. The control gate 18 is formed by depositing a conductive layer on an entire surface of the silicon substrate 10 and patterning the deposited conductive layer.
In such a flash memory, however, probability that electrons will move to the control gate 18 at a sharp edge of the floating gate 14 is increased. This represents that the electrons retained in the floating gate 14 move to the control gate 18, and it also means data loss. Consequently, the reliability of data retention in the flash memory device is degraded.